Spark plug



H. RABEZZANA SPARK PLUG Jan. l2, 1932.

Filed Oct. 10, 1929 gnmnffoz afro: una,

Patented Jan. 12, .Q32

' UNITED STATES PATENT OFFICE HECTOR RABEZZANA, OF FLINL MICHIGAN,.ASSIGNOR TO A C SPARK PLUG- COMPANY,

' OF FLINT, MICHIGAN, A COMPANY 0F MICHIGAN SPARK PLUG Application'filed October 10, 1929.

'lihis invention relates to spark plugs such as are used on internalcombustion engines. Ordinarily the spark plugs are simply threaded intoan opening in the engine cyline der head to position the spaced tiringpoints or spark gap thereof in the combustion chamber. Because theinter-engaging screw threads of the plug seldom make tight contact,especially if the threads are worn, the heat of combustion absorbed bythe lower end of the plug in a hot running engine is not alwaysdissipated or transferred by conduction to the water or air cooled headsu'tlicientr ly to maintain the plug at an ideal temperature, and,consequently, the plug becomes intensely hot, which results inpre-ignition as well as deterioration of the parts and other undesirabledefects.

To overcom'e the troubles and meet the conditions experienced by reasonof the poor contact between the threads in a simple and inexpensivefashion is one of the primary objects of the present invention. To thisend there is contemplated as a preferred embodiment the provision of ascrew threaded opening having a seat at its inner end beyond the threadsinto tight engagement with which, a portion at the lower end of the plugis moved when the plug is threaded into place. Thus dependence is notplaced on the fit of the threads, but al positive tight contact betweencorresponding parts of the plug and cylinder head is afforded to insurethe transterence of heat, and which, in addition, serves as a sealagainst compression losses.-

'llhe invention will best be understood upon reference to theaccompanying drawings, in which Figure 1 is a vertical sectional view ofa spark plug secured in a cylinder head in accordance with theinvention. Figure 2 is a similar sectional view of another type of plugembodying the invention, and Figure 3 is a fragmentary sectional viewillustrating a modification.

In the drawings, the reference numeral 1 indicates a cylinder headprovided with a jacket for the circulation of cooling tluid. Instead ofbeing water-cooled, the head may well be one of the air-cooled type. Thehead is provided with a screw threaded opening 2 Serial No. 398,664.

to receive the spark plug, the threads of which do not extend entirelythrough the opening but end a short distance from the inner side of thehead. Between the termination of the screw threads and the inner end ofthe opening there is provided a tapered or conical seat or shoulder 3for engagement with a similarly tapered or conical end portion 4 at thelower end of the lspark plug shell 5 and below the screw threadedportion that engages with the threads of the opening 2. l/Vithin theshell 5 is the customary insulator core 6 enclosing the centralelectrode 7 that terminates at its lower end in spaced relation with theterminal; of the electrode or wire 8 carried by the shell, the insulatorbeing secured in the shell by a bent over flange 10 at the upper end ofthe shell with suitable sealing gaskets or rings l1 and 12 interposedbetween cooperating shoulders of the core and shell. It desired, a ringor gasket 13 may be interposed between the shell and the top side of thehead l, although this may be omitted and reliance placed entirely uponthe tight contact of the portions 3 and 4 to prevent leakage. Thegasketl should be of copper or other suitable ductile material so thatit will not interfere with the tight seating ofthe lower end of theplug.

For certain types of engines the plug shown in Figure 2 has beenadopted. The only difference between this plug and that previouslydescribed is that the insulator core 15 is seated on the shell 16 closerto the bottom of the plug to reduce the path of travel of the heat takenup by the insulator tip to the water jacket. The lower portion of theshell 16 is threaded for engagement in the spark plug opening of thecylinder head 17 and provided with a tapered portion 18 below thethreads for tight seating contact with the correspondingly taperedshoulder 19. This figure also illustrates the omission of a gasketbetween the upper side of the head and the spark plug shell which washeretofore referred to.

It will be understood that the cooperating seating portions of the plugand shell need not necessarily be tapered. This is illustrated in themodified arrangement of Figure 3 where a flat shoulder 21 is providedadjacent the inner end of the spark plug opening in l the head 22 belowthe screw threads that receive the spark plug shell 23. In this case thebottom of the spark plug which is also flat seats against the shoulderupon the ad'- justment of the plug in its opening. If desired, a gasket24 of suitable ductile material may be interposed between the seatingportions of the plug and head. In this connection, it may be stated thatit might be desirable in some instances to interpose a sealing gasketbetween the contacting portions of the plug and head illustrated inFigure 1.

With the arrangement as above described,

it will be apparent that a tight contact between cooperating portions ofthe plug and head is insured and that, as a result, a more uniformdistribution of heat and a higher rate of conduction is insured than isto be had where reliance is placed solely upon lit of screw threads, ashas been the case heretofore. I claim: In an internal combustion engine,means A to facilitate heat transference between a spark plug and engineblock, including an engine block having a spark plug receiving openingtherein, whose wall consists of a screw threaded ortion extending fromits Y outer end to a point ending short of its inner end and a smoothconical seat portion immediately adjacent its inner end and between saidinner end and the screw threaded portion, and a spark plug having ashell provided with a skirt carrying screw threads for engagement in thescrew threaded portion of said opening and terminating in a smoothconical tip which is adapted to be held under pressure by screw threaden agement in tight seating contact with the con1cal endmost portion ofthe opening, whereby to permit unhindered heat flow from the lower endof the shell into the engine block.

In testimony whereof I aliix my signature.

HECTOR RABEZZANA.

